1. Field of the Invention
The present invention relates to the alkylation of paraffinic hydrocarbon feed stocks wherein an olefin is reacted with isobutane to produce an alkylate product. More particularly, the invention relates to a process for the preparation of an olefin feed by the removal of aromatic components and an alkylation process related thereto.
2. Related Information
Alkylation is the reaction of a paraffin, usually isoparaffins, with an olefin in the presence of a strong acid which produces paraffins, e.g., of higher octane number than the starting materials and which boil in range of gasolines. In petroleum refining the reaction is generally the reaction of a C3 to C5 olefin with isobutane.
In refining alkylations, hydrofluoric or sulfuric acid catalysts are most widely used. For sulfuric acid catalyzed alkylation low temperature or cold acid processes are favored because side reactions are minimized. In the traditional process the reaction is carried out in a reactor where the hydrocarbon reactants are dispersed into a continuous acid phase. In view of the fact that the cold acid process will continue to be the process of choice, various proposals have been made to improve and enhance the reaction.
As gasoline specifications further limit the quantity of olefins, aromatics and constituent vapor pressure, gasoline will continue to demand lower vapor pressure highly isoparaffinic blend component, such as alkylates. As this occurs, refiners will further convert many of their heavier olefinic streams, such as fluid cracked C5 olefin streams, to meet future gasoline specifications, and they will need a means to efficiently separate aromatic components, such as benzene, toluene and xylenes (BTX) which may be present in theses heavier olefinic feeds. In addition, some C4 olefin feeds, which are produced by dehydrogenation of butanes, may contain aromatic compounds. If not removed, these aromatic contaminants form alkyl sulfonic acids, sometimes referred to as alky sulfonates. Besides causing additional acid consumption, the by-products may cause significant issues with downstream units such as a caustic wash as it will form a stable surfactant (sodium alkyl sulfonate).